Many household electrical appliance can be hazardous if not properly used and monitored. There are many recorded instances of disastrous home fires caused by unauthorized operation of a household appliance such as a stove by children, burglars or vandals, or persons of reduced capacity or faculties such as the elderly. It is thus advantageous to be able to selectively control the use of such appliances.
In the prior art, means have been provided to prevent unauthorized usage of electrical appliances, primarily through key operated electro-mechanical circuit interrupt devices. However, such devices conventionally provide for on-off control only, meaning that the device completely interrupts the flow of electrical power to the appliance while in the interrupt or "locked" state, and it connects the appliance to the electrical supply in the operative or "unlocked" state. In the case of, for example, a stove, once the supply power has been cut off auxiliary electrical equipment such as lighting and an electrical clock also ceases to function.